This is a proposal to investigate the hypothesis that excitotoxic and oxidative cellular pathology accumulates in the brain and spinal cord during normal aging and is accentuated in age-dependent neurodegenerative disorders. The program is a continuation of our current program project, incorporating the themes of the original program and including a genetics component involving ALS with frontotemporal dementia (ALS-FTD). Project (1) will use genetic linkage analysis to identify gene defects that cause ALS-FTD. The project will also analyze the brain of spinal cords of ALS-FTD patients for patterns of oxidative injury and correlate these with the genetic data. Hypotheses: it will be possible to use contemporary human genetics to identify one or more ALS-FTD genes loci; ALS-FTD tissues will have heightened indices of oxidative toxicity. Project (2) will quantitate oxidative damage to DNA in tissues and fluids of ALS patients and determine how these vary with the illness. Parallel aims are to analyze mitochondrial DNA for mutations in neurodegenerative disorders and test the prediction that augmenting cellular energy production will slow motor neuron death in ALS mice. Hypothesis: there is an integral relationship between mitochondrial function and energy generation and the susceptibility of the brain to oxidative insults. Project (3) will use human brain tissue and a powerful system for culturing human astrocytes to investigate mechanisms whereby excitatory and oxidative stress impair normal mRNA splicing. Hypothesis: in tissues undergoing neurodegeneration defects in mRNA splicing apparatus lead to aberrant transcript splicing, altered RNA trafficking and reduced neuronal survival. Project (4) will develop and characterize a novel fusion protein composed of tetanus C and a glutamate inactivating enzyme, glutamate pyruvate transaminase (GPT). Hypothesis: tetanus C fragment will concentrate GPT at synapses and thereby reduce ambient glutamate levels and associated excitotoxicity. The project will have three cores: (1) administration and statistics; (2) molecular genetics, to test for mutations in key genes such as SOD1 or tau, and to prepare the fusion proteins for Project 4, (3) histochemistiy, to characterize panels of markers in the neural tissues of these patients. Significance: (1) Insights into the molecular causes of ALS FTD will illuminate the pathobiology of both ALS and FTD. (2) This will be one of the first comprehensive studies of mtDNA in neurodegenerative diseases, allowing direct comparisons between sequence variants in mtDNA and markers of oxidative injury. (3) These will also be among the first studies to study aberrant RNA splicing in neurons. (4) The TTC-GPT protein is a novel concept in protein delivery with potential application to many potentially neuroprotective proteins.